The characteristics of arm movements executed in unusual force environments.

Human subjects pointed at stationary visual targets without sight of their arm while the force environment was varied by applying weight or spring loads to the hand. The path travelled by the finger, pointing accuracy, and the shape of the finger velocity profile remained invariant across all force environments after a single practice trial. However, the magnitude and duration of the velocity profile depended consistently on the presence and size of a weight load. In contrast, velocity was not affected by spring loads. An analysis of movement dynamics in our study indicated that inertial and gravitational load components were compensated by separate mechanisms, the former employing time- and the latter magnitude scaling of muscle force profiles. The presence of such separate mechanisms led us to predict little problems for movement dynamics in weightlessness, which was indeed confirmed in a study on pointing movements aboard the KC-135 aircraft.     

Analog clutter cancellation algorithms for dynamic range reduction

A technique that effectively reduces the dynamic range of the input signal in a radar receiver prior to digitization is presented. The dynamic range reduction is accomplished through a process that predicts the next radar return signal from the previous return signals, generates a replica waveform, and subtracts this replica waveform from the radar return signal prior to digitization. This process allows the radar return signal to be digitized without distortion by an analog-to-digital converter (ADC) having a limited dynamic range. The full dynamic range of the radar return signal is then restored by adding the replica waveform to the ADC output. Test and evaluation results using both synthetic and recorded radar data demonstrate in excess of a 30-dB reduction in the dynamic range of the signal at the ADC input when strong clutter is present     

Results of XUV full sun imaging spectroscopy for eruptive and transient events by the spirit spectroheliograph on the CORONAS-F mission

SPIRIT (SPectroheliograph Ic soft X-Ray Imaging Telescope) is the current experiment on board theCORONAS-F satellite launched on July 31, 2001 (Oraevskii & Sobelman, 2002). The main goal of this experiment is to study a structure and dynamics of the solar atmosphere in the wide scale of heights (from the chromosphere to a far corona) and of temperatures (from ten thousands through thirty millions Kelvins) by means of the XUV imaging spectroscopy. Since the launch of the CORONAS-F satellite more than three hundred thousands of images and spectroheliograms have been recorded. For the first time continuous series of monochromatic full Sun images in MgXII lines at 8.42 Å (doublet: 8.418 and 8.423 Å) were obtained. These series include long-term continuous observations of duration up to 10 days with the cadence of 100 sec as well as temporal sequences with duration of a few minutes and high resolution of 7 sec, synchronized with flares. The spectroheliograms for the whole disk and off-limb regions are also recorded in the spectral bands 177 – 207 and 285 – 335 Å providing spectra with high resolution of various coronal structures including eruptive and transient events. This paper presents preliminary results of quick look analysis of some observational data obtained by means of the SPIRIT spectroheliographs.     

UV photobiochemistry of anhydrobiotic organisms at extremely low temperatures

Spores of Bacillus subtilis (TKJ 3412), cells of Deinococcus radiodurans R₁ (wild type) and conidia of Aspergillus ochraceus (strain 3174) have been UV irradiated (254 nm) in the dry state (3% relative humidity, argon) or in aqueous suspension at room temperature, at −55°C to −70°C and at −165°C to −170°C. The following effects have been analyzed: decrease in viability, occurrence of DNA strand breaks (pulsed-field gel electrophoresis) and production of DNA-protein cross-links (membrane filter method). The loss in viability is usually more pronounced at around −70°C than at room temperature, but it is lowest around −170°C. The kind of prevailing DNA damage varies from organism to organism. The amount of UV induced DNA-protein cross-link products steadily decreases with the temperature and is lowest at −170°C. The decrease in highly polymeric DNA by double strand breaks follows no universal pattern. The observed hypersensitivity of the three very different species at −70°C can therefore not be simply explained on the basis of the number of DNA lesions analyzed in the course of this work. We suggest that also the changing state of cellular water below and above about −130°C significantly contributes to the change in photosensitivity.     

Definition of the lower hybrid frequency by active wave methods on the intercosmos-24 satellite and comparison of these data with mass-spectrometric measurements

The lower hybrid resonance (LHR) frequency estimated from the mass-spectrometer data is compared with measurements using spectrograms of VLF noise excited by both natural sources and through active wave stimulation of the surrounding plasma. The measurements are from the Intercosmos 24 satellite taken over a 2 year period from 1989–1991.     

Confluence of navigation, communication, and control in distributedspacecraft systems

This research details the development of technologies and methodologies that enable distributed spacecraft systems by supporting integrated navigation, communication, and control. Operating at the confluence of these critical functions produces capabilities needed to realize the promise of distributed spacecraft systems, including improved performance and robustness relative to monolithic space systems. Navigation supports science data association and data alignment for distributed aperture sensing, multipoint observation, and co-observation of target regions. Communication enables autonomous distributed science data processing and information exchange among space assets. Both navigation and communication provide essential input to control methods for coordinating distributed autonomous assets at the interspacecraft system level and the intraspacecraft affector subsystem level. A technology solution to implement these capabilities, the Crosslink Transceiver, is also described. The Crosslink Transceiver provides navigation and communication capability that can be integrated into a developing autonomous command and control methodology for distributed spacecraft systems. A small satellite implementation of the Crosslink Transceiver design is detailed and its ability to support broad distributed spacecraft mission classes is described     

The effect of solar activity on ill and healthy people under conditions of nervous (correction of neurous) and emotional stresses.

It is commonly agreed that solar activity has adverse effects first of all on enfeebled and ill organisms. In our study we have traced that under conditions of neurvous and emotional stresses (at work, in the street, and in cars) the effect may be larger (~ 30%) for healthy people. Our calculations have been carried out applying the epoch-superposition method, spectrum and correlation analyses to daily data over a 1992 to 1994 period from three independent databases (Kharkiv City) on patients (adults and children) suffering from mental diseases and physical traumas. The effect is most marked during the recovery phase of geomagnetic storms and accompanied by the inhibition in the central nervous system.     

Performance evaluation of some rain rate conversion models for microwave propagation studies

An important characteristic of rainfall levels at a particular place is the statistical distribution of rainfall rate. In this paper, 5-min integration time rainfall data for the Northcentral region of Nigeria was obtained from the Tropospheric Data Acquisition Network (TRODAN), Anyigba, Nigeria. Also, 1-min integration time rainfall was measured at Minna, Nigeria. In order to obtain the optimal rain rate model suitable for this region, two globally recognised rain rate models were critically evaluated and compared with the 1-min measurements. These are the ITU-R P.837-7 and Lavergnat-Gole (L-G) models. The results obtained showed that the ITU-R P.837-7 and L-G models respectively underestimated the measured rain rate by 7.3 mm/h and 9 mm/h at time percentage exceedance of 0.1%, while they underestimated the measured rain rate by 23.4 mm/h and 13 mm/h respectively at 0.01%. At 0.001%, the measured rain rate was overestimated by the ITU-R P.837-7 and L-G models by 27.4 mm/h and 3 mm/h respectively. Further performance evaluation of the predefined models was carried out using different error metrics such as sum of absolute error (SAE), mean absolute error (MAE), root mean square error (RMSE), standard deviation (STDEV) and Spearman’s rank correlation. The results obtained adjudged the Lavergnat-Gole model as the best rain rate prediction model for this region.